The present invention generally relates to implantable cardiac stimulation leads for use with implantable cardiac stimulation devices. The present invention more particularly relates to a cardiac stimulation lead which is adaptable for either stylet placement or guidewire placement.
Implantable cardiac stimulation devices are well known in the art. Such devices may include, for example, implantable pacemakers or defibrillators. The devices are generally implanted in an upper portion of the chest beneath the skin of a patient within what is known as a subcutaneous pocket.
Traditionally, therapy delivery has been limited to the right side of the heart. To that end, one or more stimulation leads are implanted within the heart. The leads may include one or more electrodes positioned within the right ventricle or right atrium, or both, of the heart for making electrical contact with their respective heart chambers. Conductors within the leads couple the electrodes to the device to enable the device to deliver the desired cardiac stimulation therapy.
Recently, cardiac stimulation leads and methods have been proposed and even practiced for delivering cardiac stimulation therapy from or to the left side of the heart. These lead structures and methods involve lead implantation within the coronary sinus and/or the great vein of the heart and/or coronary sinus veins, for example, since the coronary sinus is closely adjacent the left atrium and extends into the great vein which is adjacent the left ventricle of the heart. Electrodes thus placed in the coronary sinus and great vein may be used for various forms of cardiac stimulation therapy such as left atrial pacing, left ventricular pacing, and even cardioversion and defibrillation, for example.
Cardiac stimulation lead placement within the left side of the heart can require lead placement in difficult to reach veins and arteries. Two methods generally practiced for lead placement are stylet placement and guidewire placement. Stylet placement is a common practice for lead placement in the right side of the heart. Guidewire placement is less commonly employed.
Currently, there is debate in the art as to which lead placement method is best for lead placement in the left side of the heart. Each has its advantages and disadvantages. Stylet placement has the advantage of simplicity and involves minimal components, a sometimes important factor during a surgical procedure. In some patients with small veins or unusual cardiac vein anatomy, the guidewire placement method may have an advantage in facilitating lead placement. It is likely that both methods will find future use.
Cardiac stimulation leads are designed for only a specific lead placement methodology. More specifically, such leads are configured for either stylet placement or guidewire placement, but not both. Unfortunately, this may result in a physician finding, during an implant procedure, that a lead already attempted to be implanted must be discarded in favor of a lead designed for a different implanting method. This not only represents additional cost, but it also can complicate the surgical procedure.
The present invention provides an elegant solution to the aforementioned problem. More specifically, the present invention provides an implantable stimulation lead which is adapted for either stylet placement or guidewire placement. Not only is the lead so adaptable, the adaptation may be made easily, requires minimal components and may be accomplished with a tool already made available to the physician.
The present invention provides an implantable cardiac stimulation lead adaptable for either stylet placement or guidewire placement. The implantable cardiac stimulation lead includes an elongated body having a distal end and a proximal end. The lead further includes at least one electrode carried by the lead body, a connector at the proximal end of the lead body, and a conductor connecting the at least one electrode to the connector. The implantable cardiac stimulation lead further includes an implanting guide structure at the distal end of the lead body. The guide structure includes a rigid member including a through bore, a plug dimensioned to be received within the through bore, and a retaining mechanism that releasably retains the plug within the through bore. When the plug is retained within the through bore, the plug is arranged to engage a stylet for stylet placement of the lead. When the plug is released from the through bore, the through bore is arranged to receive a guidewire for guidewire placement of the lead.
In accordance with a preferred embodiment of the present invention, the implanting guide structure is formed by an electrode at the distal end of the lead body. The electrode includes the through bore, the plug configured to be received within the through bore, and the retaining mechanism that releasably retains the plug within the through bore.
The retaining mechanism may include complimentary threads carried by the plug and the through bore. In addition, the conductor which connects the electrode to the connector may include a stylet coil which guides the stylet to engage the plug for stylet placement and for guiding the guidewire from the through bore to the connector for guidewire placement.
In accordance with further aspects of the present invention, the plug is arranged for receiving a tool that may be used for retaining the plug within or releasing the plug from the through bore. The connector may include a retaining element for securing the connector to an implantable cardiac stimulation device and wherein the same tool which may be used for retaining the plug within and releasing the plug from the through bore may also be used in cooperation with the retaining element for securing the connector to the implantable cardiac stimulation device.
In accordance with still further aspects of the present invention, the connector includes a through bore and a second plug is dimensioned to be received within the connector through bore and releasably retained therein by a second retaining mechanism. The second plug serves to prevent blood flow into the connector top after the lead has been positioned by guidewire placement. Alternatively, for preventing blood flow into the lead, the implanting guide structure may be arranged to receive its plug at the proximal end of its through bore. This permits the plug to be replaced in the through bore from the proximal end of the lead following a guidewire placement.